AC with PB Scaling D&D5e
This variant is meant to make all AC Calculations scale with the Proficiency Bonus (PB), making them work like Weapons, Skills, Tools, and all other Proficiencies in 5e.
PB Calculation
Reduce the original AC in -4, and if a Creature wearing such Armor/Defense is Proficient with it, they add their Proficiency Bonus to it.
For example: The original AC of Plate is 18 AC, with this change it should be 14 + Proficiency Bonus AC.
PB Calculation
Proficiency
While wearing this Armor with Proficiency, you can add your Proficiency Bonus to its calculation. If you are not Proficient with it, you do not add your Proficiency Bonus. All Creatures are Proficient with all the Unarmored Armors (such as being Unarmored, having Unarmored Defense, Mage Armor, Natural Armor, etc).
Minimum Strength
While wearing this Armor without meeting or surpassing the Minimum Strength Score required, you have Disadvantage on Strength and Dexterity Ability Checks and Saving Throws, Disadvantage on Attack rolls, you can't provide Somatic Components (such as for Casting Spells), and your Speed is reduced in -10ft (to a minimum of 5ft).
Art Credit: Military Training Ground - Lapinell